1. Field of the Invention
The present invention relates to a display system and more particularly, a method controlling a display screen.
2. Description of the Related Art
Generally, a portable terminal is equipped with various functions to perform a complex function. Recently, a dual mode portable terminal has been introduced, which can communicate through at least two wireless communication networks. Such a dual mode portable terminal can communicate by being individually connected to one wireless communication network selected by a user among a plurality of wireless communication networks. However, a mode conversion for using at least two wireless communication networks is needed in a dual mode portable terminal.
Accordingly, a dual standby portable terminal has been suggested, which can be simultaneously connected to at least two wireless communication networks. Such a dual standby portable terminal includes at least two communication modules which can be simultaneously connected to at least two wireless communication networks. Also, a dual standby portable terminal can perform a call mode through one of communication modules. That is, a dual standby portable terminal can easily change the mode for using different wireless communication networks.
However, in a dual standby portable terminal, one of the two controllers (i.e., the main controller) controls the screen, and the other controller (i.e., the sub-controller) manages the SIM (Subscriber Identity Module) and performs control regarding calls. Here, the dual standby portable terminal has two controllers having a similar structure, but a controller which controls the screen is deemed to be the main controller. Hence, after data is transmitted to the main controller using DPRAM (Dual Port Random Access Memory), the main controller performs functions related to events that have occurred with regard to a telephone, so as to display data corresponding to those events generated in the sub-controller.
Additionally, a large-capacity DPRAM is required to display a large amount of data generated by the sub-controller, thereby increasing costs, and power consumption increases as both the main controller and the sub-controller cannot enter the standby mode.